Plug and receptacle adaptors are common in the practice of interconnecting data processing and in data communication devices. One of the most common port configurations used in computing today is the serial data communication ports. It is common to physical implement such ports using the standard DB-25 connector defined in EIA Revised Standard RS-232, which standard is hereby incorporated by reference and is well known to those skilled in the art. As is well known to those skilled in the art, RS-232 defines 25 connections between data terminal equipment (DTE) and data communications equipment (DCE). As is also known to those skilled in the art, the standardization of RS-232 is honored more in the breach than in conformance. This is because the interface defined in the standard document includes a large number of signal and control lines which are superfluous to many applications. As a result of this, a number of manufacturers of data communications and terminal equipment began omitting a number of such signals. Therefore, even when the apparatus in question is interconnected physically by a DB-25 plug or receptacle, a number of the pin positions have no electrical connection thereto or a signal which is held to a particular electrical state.
The well known result of this phenomenon has been a reduction of the number of signal and control lines defined in RS-232 which are actually implemented in a number of popular and commercially successful devices. This has led to a standardized DB-9 physical connection which connects a sub-set of the 25 connections defined for the DB-25 connectors. Even more recently a popular pin configuration known as the circular 8 has been promulgated on computer serial ports by the Apple Computer Company. The circular 8 is familiar to those skilled in the art and physically resembles the DIN connector used on high fidelity audio equipment in Europe. The reduction in size of physical connections for serial communications ports, from DB-25 to DB-9 to circular 8, has been largely motivated by the need to reduce the physical size of the connectors for serial ports as data terminal equipment and data communications equipment has become smaller.
While plug to plug adaptors without intervening cable between the two ports on the adaptor are known in the art, they have generally been used for functions such as gender switching or DTE to DCE (or vice versa) conversions.
Heretofore manufacturers of one type of equipment which may be interconnected to other equipment having electrically similar but physically different connections to a serial port have either had to stock a large variety of cables to service the possible combinations of physical pin configurations which the users might encounter, or leave the users to fend for themselves in obtaining appropriate interconnect cables. Stocking a large number of cables terminated by different physical pin configurations, all of which are to perform essentially the same interconnect function, is expensive and requires significant investment in inventory, some of which may not turn over rapidly.
Additionally, well-made cables for serial ports of any significant length often cost on the order of $15 or $20 apiece.
As is also known to those skilled in the art, multi-conductor cables commonly used with serial data ports tend to have a significant weight per unit length. Placing a plug to plug or plug to receptacle adaptor, such as a gender switching device, between the physical connector to a serial port and a connector cable, provides a physically stiff and elongated structure extending out of the back of the equipment to which it is attached. The weight of the cable tends to put a significant moment on the serial port trying to rotate it around an axis in the plane of the back plate of the device to which this structure is connected. This often leads to cables falling out, unless they are secured by screws or the like.
Modems are data communications devices which, in recent years, have tended to use a small subset of the RS-232 defined signals. However, much of the equipment to which modems are connected still use DB-25 connectors. Also, it is common to connect modems to ports physically manifested by DB-9 connectors and to other physical arrangements. Therefore, there is a need in the art to provide an adaptor which is lightweight, inexpensive, designed to adapt to a large number of physical configurations, and which does not suffer the drawbacks of known cable adaptors. In particular, it is desirable that the adaptor be easily used, and it is highly desirable to have such an adaptor which forms a physically secure connection with devices to which it is attached without undue use of retaining screws and the like.